Pipe applications

The chemical inertness of polyethylene to solutions containing harsh chemicals such as inorganic acids, bases and metal salts very quickly made polyethylene a premium pipe material, accounting for the rapid use of polyethylene by the pipe manufacturers. Initial applications were in the chemical industry where the transfer of such solutions is carried out on a routine basis. A representative list of some of the chemicals that are inert to polyethylene for pipe applications is shown below [1]. 

Examples of Harsh Chemical Solutions Inert to Polyethylene 

Ammonium hydroxide Calcium hypochlorite Nitric acid Sea water Sulfuric acid Chromic Acid Hydrogen peroxide Potassium hydroxide 

In many cases polyethylene had a significant cost advantage over other pipe materials such as stainless steel and copper tubing. 

Polyethylene rapidly displaced other materials for electrical applications due to their significantly improved properties for this application. Growth of over 400%, from 35 million Ibs/year inl956 tol90 million Ibs/year in 1960, was achieved. The important product attributes for electrical applications are summarized below. 

---

R. A. Ereggens, Experimental Determination of Wick Propertiesfor Heat Pipe Applications, ST-4086, RCA Electronics Components, Lancaster, Pa., 1969. 

Coupolet- fittiiigs are uesigned mr us r protection sprinkler systems and other low pressure piping applications. 

Polypropylene (PP) is a crystalline polymer suitable for low-stress applications up to 225°F (105°C). For piping applications this polymer is not recommended above 212°F (100°C). Polypropylene is shielded, pigmented, or stabilized to protect it from uv light. Polypropylene is often a combination of polyethylene and polypropylene which enhances the ductility of the polymer. 

A typical piping application starts with a specified flow rate for a given fluid. The piping system is then designed with the necessary valves, fittings, etc. and should be sized for the most economical pipe size, as discussed in Chapter 7. Application of the energy balance (Bernoulli) equation to the entire system, from the upstream end (point 1) to the downstream end (point 2) determines the overall net driving force (DF) in the system required to overcome the frictional resistance ... 

Baldyga, I., and Henczka, M., Turbulent mixing and parallel chemical reactions in a pipe application of a closure model, Recents Progres en Genie des Procedes 11, 341-348 (1997). Bermingham, S. K., Kramer, H. I. M., and Van Rosmalen, G. M. Comp. Chem. Eng. 22, 355-362... 

A 105 Carbon Steel Forgings for Piping Applications [Note (2)]... 

This Nonmandatory Appendix provides guidance in the form of precautionary considerations relating to hydrogen service and piping applications. These are not Code requirements but should be taken into account as applicable in the engineering design. Further information on these subjects can be found in the literature. 

ASTM A 105, Standard specification for carbon steel forgings for piping applications. 

In many FGD pipe applications, 40 durometer pure gum rubber gives only 3-7 years of service, whereas a 60 durometer natural rubber gives 7-10 years of life. Since most FGD scrubber piping encounters very light abrasion, installing chlorobutyl is expected to last in excess of 15 years. Chlorobutyl is better for the absorber and the demister supporters as the performance lining. 

J. Scheirs, L.L. Boehm et al., PE100 Resins for Pipe Applications Continuing the Development into the 21st Century, Elsevier 1996, TRIP, Vol. 4, No. 12. 

The newer open-cell foams, based on polyimides (qv), polybenzimidazoles, polypyrones, polyureas, polyphenylquinoxalines, and phenolic resins (qv), produce less smoke, are more fire resistant and can be used at higher temperatures. These materials are more expensive and used only for special applications including aircraft and marine vessels. Rigid poly (vinyl chloride) (PVC) foams are available in small quantities mainly for use in composite panels and piping applications (see Flame retardants Hrat-rrststantpot.ymf.rs). 

In most process piping applications, the required Kenics mixer diameter is the same as the existing process line diameter. The K-factor for a specific process application is determined by the Reynolds number as follows [35] ... 

Vasiliev L.L., Kulakov A.G. (2003) Heat Pipe applications in sorption refrigerators, Low Temperature and Cryogenic Refrigeration. NATO Science Series II, Vol 99, Kluwer Academic Publishers, 401- 414. 

The application of hydrogen peroxide for environmental clean-up has a pivotal role to play within the chemical industry. Indeed, such treatments have breathed new life into industries which have been classed as damaging to the environment, thus extending their lifetime. Whilst it will always be desirable to aim for zero effluent processes, it is only realistic to have in the armoury the ability to treat waste products end of pipe . Such end of pipe applications for peroxy-gens will enable more economic routes to industrially important products to be developed. 

This review has highlighted several aspects of the toughness of / -nucleated PP. Although its long-term behavior because of its relevance in pipe applications has been outlined, the focus has been on dynamic fracture properties, a topic which has been largely documented in the literature. Ductile-brittle... 

Medium Density High Density Polyethylene MDPE (or MDHDPE) is produced by copolymerization of ethylene with a-olefins using Ziegler-Natta, supported chromium or single site catalysts. MDPE cannot be produced by free radical polymerization. MDPE has a linear structure similar to LLDPE, but comonomer content is lower. Density is typically 0.93-0.94 g/cm. MDPE is used in geomembrane and pipe applications. 

Pervaporation occupies a special niche in the chemical industry—it is the only membrane process primarily used to purify chemicals. At the start of 2000, about 100 pervaporation units were operating worldwide, most of them dehydrating solvents, such as ethanol and isopropanol. Now that pervaporation has been proven in these end-of-pipe applications, attention is being focused on large-scale separations that are closer to the chemical reaction step—to be more critical for production and to bring much greater benefits. 

Lead stabilizers are primarily used in wire and cable and in rigid pipe applications. 

An example system is PVC and polyethylene wire and cabling irradiated to improve stresscracking resistance, abrasion resistance, high-temperature properties and flame retardance, via controlled electron-beam crosslinking (Loan, 1977). Additionally electron-beam crosslinking is utilized to impart memory into a polymer system, such as crosslinked PE materials for heat-shrinkable films and pipe applications (Baird, 1977). The control of electron-beam processing has advanced the quality of cell size and shape of PE foams via control of crosslink distribution (Paterson, 1984). 

Industrial usage includes a variety of tank, vessel, and piping insulation. The PIR foams are often preferred, because of their higher continuous service temperature (150 C). Cut and preshaped slabstock is used for many industrial plant piping applications. The foam spraying of tanks and pipelines is getting considerable attention in the Middle East and African markets. 

R. A. Freggens, Experimental Determination of Wick Properties for Heat Pipe Applications, Proc. 4th Intersoc. Energy Conversion Eng. Conf, Washington, DC, pp. 888-897,1969. 

---